French psychiatrists' unions have reacted angrily after a doctor was found guilty of manslaughter because her patient hacked an elderly man to death.

In the first case of its kind in France, Daniele Canarelli, 58, a psychiatrist based at the Edouard-Toulouse hospital in Marseille, was sentenced to one year's suspended prison sentence as judges said she had committed the "grave error" of failing to recognise the public danger posed by Joel Gaillard, her patient of four years.

Gaillard, 43, had escaped from a hospital consultation with Canarelli in February 2004 and 20 days later he used an axe to kill the 80-year-old partner of his grandmother in Gap in the Alps region. Gaillard, who suffered from a kind of paranoid schizophrenia, had been seeing the consultant for four years and had already been forcibly committed to a secure hospital on several occasions for a series of increasingly dangerous incidents.

The court said Canarelli should have requested Gaillard be placed in a specialised medical unit or referred him to another medical team, as one of her colleagues suggested. Her refusal had equated to a form of "blindness", the court president, Fabrice Castoldi, said.

Defence lawyers warned that the ruling would have serious repercussions for treatment of the mentally ill. "If a psychiatrist lives in fear of being sentenced, it will have very real consequences and probably lead to harsher treatment of patients," Canarelli's lawyer, Sylvain Pontier told Reuters.

The victim's son, Michel Trabuc, said he hoped the case would set a legal precedent. "There's no such thing as zero risk, but I hope this will move psychiatry forward and, above all, that it will never happen again," he said.

Gaillard was found criminally irresponsible for his actions and is currently in a psychiatric hospital.

SPEP, the union for French state psychiatrists, which backed Canarelli during the trial, said the landmark verdict was worrying and risked scapegoating the profession over a complex case. The union said Canarelli had notified police and other authorities after her patient's escape.

On the first day of the trial, psychiatric medial staff had protested outside court with banners, including one reading: "Dark day for psychiatry".